This invention relates to a method of decreasing fatigue in humans who switch their circadian rhythm reference times. More particularly, the invention is concerned with reducing fatigue in a human by administering hydrocortisone.
In the following description, certain references are mentioned. These are described at the end of the specification.
The need to be alert and competent on night duty in a profession that requires episodic night shifts is a major issue among emergency physicians, as with many professions in the modern industrial age.sup.1. Emergency physicians report substantial career dissatisfaction because of the burden of dealing with night shifts and the accompanying sleep disturbances.sup.2. Administration of hydrocortisone has not been used to decrease the perception of stress and improve mood during night shifts whereas melatonin has been evaluated as an endocrine intervention with variable findings.sup.3,4,5.
The literature demonstrates greater accident rates on night shifts.sup.6. Physicians could be prone to that same tendency to error. The need to be alert, awake and competent, regardless of work shift is important to the customer of the night worker, just as the fatigue of the job is important to the worker.
To date, no studies exist in which hydrocortisone has been used as a means of assisting in the "phase shift". There are many descriptive studies on the circadian rhythms of shift workers, of airline stewardesses and others exposed to alterations in the normal human day-night cycle, either shift or meridian change suggesting that there is a good deal of fatigue and stress involved.
The fatigue of night duty has been clearly documented in the medical literature. Approximately 7.3 million American workers have night duty as part of their jobs.sup.7 and rarely make a complete adaptation to night duty and day sleep .sup.8,9,10. As an expected consequence, work related accidents are far more frequent on the night shift.sup.11,12. The U.S. Dept. of Transportation reports that up to 200,000 traffic accidents each year may be sleep related and that 20% of all drivers have dozed off at least once while behind the wheel.sup.13. Though causes of major industrial accidents are always complex, it should be noted that Three Mile Island, Bhopal, Exxon Valdez and Chernobyl all occurred on the night shift. These events only raise the importance of addressing the issue of human adaptation to night duty as society emerges from a diurnal work place to the 24-hour industrial age.
Czeisler and Johnson reported on a physiologic method of adapting to night work.sup.14, though their method required at least 4 days before physiologic adaptation occurred. They used bright lights during the night and complete dark during the day. This demonstrated that it takes time to adapt even with an efficient and carefully orchestrated protocol. This study did not address the need of managing the episodic single night which is the reality for many industrial age workers.
Moore-Ede and Schmelzer demonstrated in squirrel monkeys that cortisol mediates the synchronization of circadian rhythms.sup.15. Czeisler has shown that cortisol levels are at their nadir during the night hours, that cognitive performance and alertness decline during the progression of night hours to a nadir at 4-8 hours after midnight.
The effects of poor performance are not just transient. Moore-Ede has proposed the concept of a "shift maladaption" syndrome to describe the clinical pathologies observed in long time shift workers.sup.16. The consequences of repeated shift work over years have been poorly documented but include sleep-wake disorders, gastrointestinal pathology, and an increased risk of cardiovascular disorders.sup.17. Moore-Ede notes the extraordinary difficulty in studying night workers as they tend to be young, with few medical problems by merit of age. They tend to shift to day jobs as they gain seniority which invalidates longitudinal studies. Moore-Ede notes that the problems of jet leg, the physiological equivalent of shift work, are short term.sup.17.
The ability of humans to adapt to a shift in circadian systems is limited. It can only be reset by a few hours a day and therefore has a limited "range of entrainment".sup.18. The typical range of entrainment is approximately 23.5 to 26.5 hours for the synchronized human system, allowing a "phase advance" of 0.5 hours per day or a "phase delay" of 2.5 hours per day.sup.11.
To date, no good research exists as to the length of the "average career length" of emergency physicians because the field is new. Experts in the field suggest lengths of 9-12 years prior to "burnout" and movement into other fields of medicine.sup.17,19. The need for Emergency Physician to remain alert and functionally competent is self-evident.sup.20, 21. The correlation between the stress of nights and the longevity of career is also obvious.sup.22.
It is therefore an object of the invention to provide a method of decreasing fatigue in humans.
It is also an object of the invention to provide a method of alleviating the effects of jet lag.